I ended up using a SharedInformer.
These resources were helpful.
.
package main
import (
"encoding/json"
"errors"
"flag"
"fmt"
"io/ioutil"
"k8s.io/api/apps/v1"
metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
"k8s.io/apimachinery/pkg/types"
"k8s.io/client-go/informers"
"k8s.io/client-go/kubernetes"
"k8s.io/client-go/tools/cache"
"path/filepath"
"strings"
// We need this import to load the GCP auth plugin which is required to authenticate against GKE clusters.
_ "k8s.io/client-go/plugin/pkg/client/auth/gcp"
"k8s.io/client-go/tools/clientcmd"
"log"
"os"
)
const manifestsDir = "manifests"
// Use an empty string to run on all namespaces
const namespace = ""
const newLabelKey = "new-label-to-add"
const tempLabelKey = "temporary"
const tempSuffix = "-temp"
const componentLabelKey = "component"
func main() {
var kubeconfig *string
if home := homeDir(); home != "" {
kubeconfig = flag.String("kubeconfig", filepath.Join(home, ".kube", "config"), "(optional) absolute path to the kubeconfig file")
} else {
kubeconfig = flag.String("kubeconfig", "", "absolute path to the kubeconfig file")
}
flag.Parse()
// use the current context in kubeconfig
// TODO (dxia) How can I specify a masterUrl or even better a kubectl context?
cfg, err := clientcmd.BuildConfigFromFlags("", *kubeconfig)
exitOnErr(err)
kubeclient, err := kubernetes.NewForConfig(cfg)
exitOnErr(err)
fmt.Printf("Getting deployments with '%s' label.
", componentLabelKey)
deployments, err := kubeclient.AppsV1().Deployments(namespace).List(metav1.ListOptions{
LabelSelector: componentLabelKey,
})
fmt.Printf("Got %d deployments.
", len(deployments.Items))
exitOnErr(err)
deployments = processDeployments(deployments)
fmt.Println("Saving deployment manifests to disk as backup.")
err = saveDeployments(deployments)
exitOnErr(err)
tempDeployments := appendToDeploymentName(deployments, tempSuffix)
tempDeployments = createDeploymentsWithNewLabel(tempLabelKey, "true", tempDeployments)
factory := informers.NewSharedInformerFactory(kubeclient, 0)
informer := factory.Apps().V1().Deployments().Informer()
stopper := make(chan struct{})
defer close(stopper)
informer.AddEventHandler(cache.ResourceEventHandlerFuncs{
AddFunc: func(obj interface{}) {
d := obj.(*v1.Deployment)
labels := d.GetLabels()
if _, ok := labels[tempLabelKey]; ok {
labelsStr := joinLabelKeyVals(labels)
fmt.Printf("2: Temporary deployment created in namespace %s, name %s, labels '%s'.
", d.GetNamespace(), d.GetName(), labelsStr)
deploymentToDelete := strings.Replace(d.GetName(), tempSuffix, "", -1)
deployment := getDeployment(d.GetNamespace(), deploymentToDelete, componentLabelKey, kubeclient)
if deployment != nil {
fmt.Printf("3: Now deleting previous deployment in namespace %s, name %s.
", d.GetNamespace(), deploymentToDelete)
if err := deleteDeployment(d.GetNamespace(), deploymentToDelete, kubeclient); err != nil {
exitOnErr(err)
}
} else {
fmt.Printf("4: Didn't find deployment in namespace %s, name %s, label %s. Skipping.
", d.GetNamespace(), deploymentToDelete, componentLabelKey)
}
} else if labelVal, ok := labels[newLabelKey]; ok && labelVal == "production" {
fmt.Printf("Normal deployment with '%s' label created in namespace %s, name %s.
", newLabelKey, d.GetNamespace(), d.GetName())
deploymentToDelete := d.GetName() + tempSuffix
fmt.Printf("6: Now deleting temporary deployment in namespace %s, name %s.
", d.GetNamespace(), deploymentToDelete)
if err := deleteDeployment(d.GetNamespace(), deploymentToDelete, kubeclient); err != nil {
exitOnErr(err)
}
}
},
DeleteFunc: func(obj interface{}) {
d := obj.(*v1.Deployment)
labels := d.GetLabels()
if _, ok := labels[newLabelKey]; !ok {
if _, ok := labels[tempLabelKey]; !ok {
fmt.Printf("Deployment without '%s' or '%s' label deleted in namespace %s, name %s.
", newLabelKey, tempLabelKey, d.GetNamespace(), d.GetName())
fmt.Printf("5: Now creating normal deployment with '%s' label in namespace %s, name %s.
", newLabelKey, d.GetNamespace(), d.GetName())
deploymentToCreate := createDeploymentWithNewLabel(newLabelKey, "production", *d)
if err := createDeploymentOnApi(deploymentToCreate, kubeclient); err != nil {
exitOnErr(err)
}
}
}
},
})
fmt.Println("1: Creating temporary Deployments.")
err = createDeploymentsOnApi(tempDeployments, kubeclient)
exitOnErr(err)
informer.Run(stopper)
}
func getDeployment(namespace string, name string, labelKey string, client *kubernetes.Clientset) *v1.Deployment {
d, err := client.AppsV1().Deployments(namespace).Get(name, metav1.GetOptions{})
if err != nil {
return nil
}
if _, ok := d.GetLabels()[labelKey]; !ok {
return nil
}
return d
}
func createDeploymentWithNewLabel(key string, val string, deployment v1.Deployment) v1.Deployment {
newDeployment := deployment.DeepCopy()
labels := newDeployment.GetLabels()
if labels == nil {
labels = make(map[string]string)
newDeployment.SetLabels(labels)
}
labels[key] = val
podTemplateSpecLabels := newDeployment.Spec.Template.GetLabels()
if podTemplateSpecLabels == nil {
podTemplateSpecLabels = make(map[string]string)
newDeployment.Spec.Template.SetLabels(podTemplateSpecLabels)
}
podTemplateSpecLabels[key] = val
labelSelectors := newDeployment.Spec.Selector.MatchLabels
if labelSelectors == nil {
labelSelectors = make(map[string]string)
newDeployment.Spec.Selector.MatchLabels = labelSelectors
}
labelSelectors[key] = val
return *newDeployment
}
func createDeploymentsWithNewLabel(key string, val string, deployments *v1.DeploymentList) *v1.DeploymentList {
newDeployments := &v1.DeploymentList{}
for _, d := range deployments.Items {
newDeployment := createDeploymentWithNewLabel(key, val, d)
newDeployments.Items = append(newDeployments.Items, newDeployment)
}
return newDeployments
}
func setAPIVersionAndKindForDeployment(d v1.Deployment, apiVersion string, kind string) {
// These fields are empty strings.
// Looks like an open issue: https://github.com/kubernetes/kubernetes/issues/3030.
d.APIVersion = apiVersion
d.Kind = kind
}
func processDeployments(deployments *v1.DeploymentList) *v1.DeploymentList {
newDeployments := &v1.DeploymentList{}
for _, d := range deployments.Items {
// Set APIVersion and Kind until https://github.com/kubernetes/kubernetes/issues/3030 is fixed
setAPIVersionAndKindForDeployment(d, "apps/v1", "Deployment")
d.Status = v1.DeploymentStatus{}
d.SetUID(types.UID(""))
d.SetSelfLink("")
d.SetGeneration(0)
d.SetCreationTimestamp(metav1.Now())
newDeployments.Items = append(newDeployments.Items, d)
}
return newDeployments
}
func saveDeployments(deployments *v1.DeploymentList) error {
for _, d := range deployments.Items {
if err := saveManifest(d); err != nil {
return err
}
}
return nil
}
func saveManifest(resource interface{}) error {
var path = manifestsDir
var name string
var err error
switch v := resource.(type) {
case v1.Deployment:
path = fmt.Sprintf("%s%s/%s/%s", path, v.GetClusterName(), v.GetNamespace(), "deployments")
name = v.GetName()
default:
return errors.New(fmt.Sprintf("Got an unknown resource kind: %v", resource))
}
bytes, err := json.MarshalIndent(resource, "", " ")
if err != nil {
return err
}
err = os.MkdirAll(path, 0755)
if err != nil {
return err
}
err = ioutil.WriteFile(fmt.Sprintf("%s/%s", path, name), bytes, 0644)
if err != nil {
return err
}
return nil
}
func deleteDeployment(namespace string, name string, client *kubernetes.Clientset) error {
if err := client.AppsV1().Deployments(namespace).Delete(name, &metav1.DeleteOptions{}); err != nil {
return err
}
return nil
}
func appendToDeploymentName(deployments *v1.DeploymentList, suffix string) *v1.DeploymentList {
newDeployments := &v1.DeploymentList{}
for _, d := range deployments.Items {
d.SetName(fmt.Sprintf("%s%s", d.GetName(), suffix))
newDeployments.Items = append(newDeployments.Items, d)
}
return newDeployments
}
func createDeploymentOnApi(d v1.Deployment, client *kubernetes.Clientset) error {
d.SetResourceVersion("")
if _, err := client.AppsV1().Deployments(d.GetNamespace()).Create(&d); err != nil {
return err
}
return nil
}
func createDeploymentsOnApi(deployments *v1.DeploymentList, client *kubernetes.Clientset) error {
for _, d := range deployments.Items {
if err := createDeploymentOnApi(d, client); err != nil {
return err
}
}
return nil
}
func joinLabelKeyVals(labels map[string]string) string {
labelKeyVals := make([]string, 0, len(labels))
for k, v := range labels {
labelKeyVals = append(labelKeyVals, fmt.Sprintf("%v=%v", k, v))
}
return strings.Join(labelKeyVals, ", ")
}
func homeDir() string {
if h := os.Getenv("HOME"); h != "" {
return h
}
return os.Getenv("USERPROFILE") // windows
}
func exitOnErr(err error) {
if err != nil {
log.Fatal(err)
}
}
